Process for the treatment of coal tar oil



Patented July 23,. 1946 UNITED STATES raocnss Foa 'rmi mamnror coal.

- 'ran. on.

' nei-tert Koelhel, mete, Ne aei-iieim, Germany No matting. Ap'pii'eititii September :1, 1m.

gsegial No. 164,985. In Germany Septembu M,

a Claims. (Cl. 196-401 The present known processes for the treatment of coal tar oil or of tar oils of similar composition, such as fractional distillation or acid treatment, yield products which are'suitable for a 5 great variety of purposes.v But the degree of purity of the tar oils obtained in this manner is not sufficient to permit their use as motor fuels, particularly for Diesel engines. The object of the present invention is to purify coal tar oils 9 or similar tar oils to such an extent that they may be used as a 'motor fuel for Diesel engines. It is already known that primary tars may be purified by heating them with 78% sulphuric acid monohvdrate to 180 C. to enable the oils,

to be used as solvents or forthe manufacture of lubricants. Attempts have been made in the same way to improve the odour of heavy tar oils by treating them at 80-90 C. with 50-60% sulphuric acid monohydrate. Primary coal tar oils free from bases and phenols, with a boiling range of 100-200 C. have also been purified by treatment with concentrated sulphuric acid diluted with paraflin oil, followed immediately by dis-' tillation. For the manufacture of lubricating 28 oils, products of hydrogenation under pressure,

more particularly products obtained by hydrogenation of coal, have also been treated by solution in organic media and by treatment with'diluted mineral acids.

39 It is true that with these processes-partly intended for oils of a composition different from that of the coal tar oilit is possible to attain a degree of purity that is requisite for some desired purpose, but such processes are not practical 86 for producing therefrom Diesel motor fuel. A

special process of purification is necessary for removingfrom the tar oils -theundesirable asphalt', resin and pitch ingredients and more par:-

ticularly the phenolic substances, which when 40. present in Diesel fuel causeiormation of resin and coke.

These disadvantages are eliminated by the process of treatment according to my'invention in which the coal tar oils to be treated are mixed I with mixtures of paraflln hydrocarbons, the' boiling range of which is between 180-350 0., and this mixture is treated at room temperaturefor a short time with diluted acid until a complete reaction has been effected. After setup tling or centrifuging, the following three layers are produced, 1. e., v

,,(1) A mixture of tar oil'and parailinic hydrocarbons,

(2) Acid, and I ll (3) Sediment, which three layers can be easily separated from each other in any known manner.

The mixture under (1) can be completely deaoid ified by repeated washing, dried, and if Q desired bleached. i 1

It has been found particularly advantageous in the manufacture according to my invention of Diesel fuel, to mix the coal tar oils with paraf-' flnic hydrocarbons of the boiling'range of 180- 350 C. obtained from benzine synthesis by the I Fischer-Tropsch process. This hydrocarbon fraction which differs from the natural products of the same boiling range by its purely paraffinic structure (recognizable by.the extraordinarily low specific gravity of 0.7-1 (15 (2.)), of- 10 fers considerable motor advantages" by reason of its readiness to ignite and its clean combusion. I'he chemical advantages derived from the use of this synthetic product in the process are that the tar .oil is dissolved in such a manner that its desirable constituents pass into solution while the undesirable constituents are eliminated by the action of the sulphuric acid. I

The use heretofore of fuel mixtures containing tar oils proved a failure owing to the relatively high proportion of resin, pitch and asphalt therein, and thus their use as motor fuels ,was imprac- V ticable and their keeping properties were im-' paired.

The proportion of phenol or phenolic oils'present therein would cause'the formation of coke in the combustion chamber of the Diesel engine, or the injection nozzles would become clogged by resinification. With the acid treatment accord- 80 ing to the present invention it is possible to remove the greater part of these phenols or phenolic oils so that the above mentioned draws backs are mostly eliminated.

The acids which are readily separated after the treatment, may be utilized again for treating a fresh quantity of the mixture. If the process is effected in several stages, the acid which has already been used may be returned to the first stage of purification. 40

As the' sediment easily separates on the one hand from the tar oil-,hydrocarbon mixture, and on the other hand from the acids, it is readily available for further treatment. Such treatment can be eifected either by-a mechanical method, for instance, by solution, extraction or distillation, or. by a chemicalmethod, for instance by acid-treatment, treatment with lye, or by cracking.

As compared with theusual treatment of tar oils with concentrated acids, the diluted acids used in my process according to the invention are readily recoverable and can be returned into-the process without any special treatment. 'Moreover the refining losses are substantially smaller than when using concentrated acids.

The use of the process according to the present invention offers the advantages of small consumption of acid, small'reflning losses, ready separation of the desired constituents, ready separation of the undesirable constituents, more particularly elimination of the phenolic con-- stituents, and recovery ofthe acids.

The following example serves to illustrate how the invention can be carried into effect.

35 kgspof a coal tar'oil having-a boiling point between 180-350 C.,*a.nd 17 kgsiof a paraflln oil having a boiling point within the same range,

such as obtained for instance by the Fischer and Tropsch process, are mixed, together, and this mixture, withoutbeing heated, is shaken for a short time with about 15.1itres of 20% sulphuric The mixture I layers. The upper one contains the considerably lighter-coloured. refined oil, ,the central layer contains the light yellow-coloured sulphuric. acid, and the bottom layer contains the separated dark impurities constituting the sediment.

The three layers are separated from each other.

' About 47 kg's. of the refined oil fromthe upper layer and'5 kgs. of the separated impurities are obtained-which can-be treated to provide phenols or heating oil. The acid which has been employed is used for the purification of further mixtures. The refined oil is washed in the usual I manner; if desired it may be, further purified, in 1, which case.treatment with-bleaching earth is I particularly advantageous.

separates immediately, into three mixing with the tar oils, paraflinic hydrocarbons having a boiling range between180 C. and 380 C., treating the mixture with diluted sulphuric carbons having 'aboiling range between 180 C.

" The application of bleaching earth on the mixture before the action of the acid, has no visible effect. The refined oil can be utilised at once as Diesel fuel. A comparison of the chemical and physical properties of the mixture before and after the use of the process shows the advantages obtained.

Chemical-physical data of tar oil-parafiin hydrocarbon mixtures.

Before treat- After treatment ment Density at 20 0.950 0. 933 Viscosity 1.33 E,20 C. 1.32 E, 20 C. Spec. parachor. 24.14 23. 48 Separation at. degrees 6 8 Hard asphalt contentnupercentfl 0. 24 0.06 Coking residue -.do. 0. 40 0. 09 Phenol content volume percent" '5. 6 l. 2

The refined oil may be effectively used as motor fuel, since the purification as shown by the above analysis results in the reduction of the density from 0.950 to 0.933 and the consequent loweringof the specific parachor, obtained by the elimination of impurities having specific gravities of over" 1.0, thereby I providing a Diesel fuel having a greater readiness to ignite and having better combustion properties. The reduction of viscosity gives better spraying qualities. The reduction of the hard asphalt content from 0.24 to 0.06% for thefirst time enables this mixture to be used as motor fuel, sincethe risk of carbonization in the combustion chamber and of the clogging the nozzles as well as of scoring of the pistons, is eliminated by thetreatm'entaccording to my inven-. 1

tion. The same advantage is expressed by the reduction of the coking residue from 0.40 to 0.09%.. A very important advantage is the considerablereduction of, the phenol content, as

phenols in Diesel fuels easily lead to resinification' and nozzle clogging, as well as to corrosion and piston scoring.

What I claim is:-

a 1. Aprocess for treating tar oils to render them suitable for use as motor fuels particularly for j Diesel engines, which comprises the steps of adand 380 C.', treating the mixture with diluted sulphuric acid of substantially 20% concentration at ordinary temperature, anl separating the upper stratum of refined oilfrom the intermediate sulphuric acid stratum and the bottom sediment stratum. 1 Y

-3.. A process for treating tar oils to render them suitable for use as motor fuels particularly for Diesel engines which comprises the steps of admixing with the tar oils, paraffinic hydrocarbon mixtures obtained in the benzine'synthesis according to Fischer and ,Tropsch, treating the mixture with diluted sulphuric acid of substantially 20% concentration at ordinary temperature, and separating the upper'stratum of refined oil from the intermediate sulphuric acid layer and the bottom sediment stratum.

4. A process for treating coal tar oils to render them suitable for use as motor fuels particularly for Diesel engines which comprises the steps of admixing with the coal tar oils, paraflinic hydrocarbon mixtures obtained in the benzine synthesis according to Fischer and Tropsch, treating the mixture with diluted sulphuric acid of substantially 20% concentration at ordinary temperature, and separating the upper stratum of refined oil from the intermediate sulphuric acid stratum and the bottom sediment stratum.

5. A process for treating tar oils to render them suitable for use as motor fuels particularly for Diesel engines, which comprises the steps of admixing with the' tar oils, paramnic hydrocarbons having a boiling range between 180 C. and 380 C., treating the mixture with diluted sulphuric acid of substantially 20% concentration at ordinary temperature, separating the upper stratum of refined oil from the intermediate sulphuric acid stratum and the bottom sediment stratum, washing and drying the refined oil and treating it with bleaching earth. I

6. A process for treating coal tar oils to render them suitable for use as motor fue1s particularly for Diesel engines, which comprises the steps of admixing with the coal tar oils, paraflinic hydrocarbons having a boiling range between 180 C. and 380 C., treating the mixture with diluted sulphuric acid of substantially20% concentration at ordinary temperature, stratum of refined oil from the intermediate sulphuric acid stratum and the bottom sediment stratum, washing and drying-the refined oiland treating it with bleaching earth.

7. A process for treating tar oils to render them suitable for use as motor fuels particularly for Diesel engines, which comprises the steps of admixing with the tar oils, paraflinic hydrocarbon mixtures obtained in the benzine synthesis according to Fischer and Tropsch, treating the mixture with diluted sulphuric .acid of substantially 20% concentration at ordinary temperature, separating the upper stratum of refined oil from the intermediate sulphuric acid stratum and the separating the upper' the mixture with sulphuric acid 0! sub stantially 20% concentration at ordinarytem- "perature, separating the upper stratum oi refined oil from the intermediate sulphur acid stratum and the bottom sediment stratum, washing and drying the refined oil: and treating it withbleachv lug-earth. v 4

- HERBERT KOEHBEL, 

